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In summer 2011, a team of 25 masons began cladding the facade of Stokes Hall, the University’s new 183,000-square-foot academic building. When the job is done, in late fall, they will have laid approximately 11,000 pieces of limestone and 44,000 pieces of granite, covering some 55,000 square feet of walls, gables (13), arches (nine), and window frames (550).
Preparations commenced in 2010, when representatives from Boston College and the architectural firm Tsoi/Kobus selected granite from a quarry in York, Maine, called Old York Blend, compatible in color and texture with the stonework on adjacent McElroy Commons and Lyons Hall. (Stone was not always imported to the Heights. It is likely that Gasson Hall, the first building erected, included stones excavated or found on-site—the remains of walls and old foundations.)
About the same time the granite was selected, the architect and contractors chose an Indiana limestone and picked out approximately 25,000 cubic feet of quarried stone that had been seasoned in the open air for one year. Seasoning allows “quarry sap”—trapped moisture that contains discoloring organic matter—to leach out. A fabricator in Minnesota milled and sculpted the limestone into arches, window frames, ornamental panels, and quoins, numbering each finished piece according to its destination on the building’s exterior.
The granite and limestone facade is just that, a facade. It cloaks—but does not directly touch—a structural wall of reinforced concrete blocks. This concrete wall is clothed with a waterproof membrane that is, in turn, covered in blue foam insulation panels. The exterior stonework sits two-to-three inches of open space away from the insulated concrete, secured to the support wall by metal anchors fixed in the exterior wall’s mortar and screwed into the concrete.
The granite slabs weigh between 20 and 150 pounds each. Workers on the ground assemble pallets of stones for the area under construction using printouts of a template to guide their choice of size and color. Before setting the pieces in place by hand, the masons bevel the stones’ edges to produce a smooth visual transition between pieces and, as needed, excavate depressions to create visual “depth” in the wall’s profile. “They put the chisel to every piece,” says Brian Black, the on-site masonry manager. A three-man team can build some 400 square feet of granite wall in a week.
After four weeks of curing, the new masonry is gone over with brushes and detergent to clean off stray bits of mortar and other debris. The facade should be good for at least a hundred years.
Read more by Thomas Cooper